WEDNESDAY, March 27 (HealthDay News) -- People who have been mugged or randomly attacked can remain highly distrustful of others long after the incident, a new study finds.

The findings reveal a previously under-recognized effect of physical assault and could help improve therapy for victims, the British researchers said.

Their study included more than 100 people treated at a hospital for minor injuries suffered during a mugging or physical assault. The participants were monitored for the next six months.

Four out of five victims said that since the assault, they were more fearful of other people than they wanted to be, according to the study, which was published March 27 in the journal Psychological Medicine.

Factors that resulted in strong feelings of mistrust lasting for six months included: being attacked close to home, feeling defeated at the time, excessive worry afterward, feeling unsupported by others and sleeping problems.

It is well known that suffering a physical assault can cause symptoms of
post-traumatic stress disorder, but this is the first study to show that excessive mistrust of other people, or paranoia, can last for months after an assault, the researchers said.

"It is very understandable that being attacked makes us wary of the people around us. Our mindset may become more like that of a bodyguard, vigilant for danger," study leader Daniel Freeman, a professor at the University of Oxford, said in a Wellcome Trust news release.

"When we are overly mistrustful, that is a form of paranoia," Freeman said. "It may well be a normal temporary change in our thinking after being a victim of attack."

The danger of such thoughts, however, is that people may end up isolating themselves from others and dwell only on the worst, said Freeman, who led the study while at the Institute of Psychiatry of King's College London.

"It is an under-recognized problem in the aftermath of an attack," he said.